The present invention relates to an inertia damper for preventing vibration of a rotary shaft of an apparatus such as, for example, a stepping motor or the like which frequently repeats start and stop motions.
In the stepping motor, the rotation should accurately follow the input pulse and it is necessary to eliminate resonance and an unstable phenomenon which may be caused during operation.
Therefore, it is necessary to reduce the braking time which is the transient response characteristic of the stepping motor and such reduction can be achieved by quickly controlling the vibration of the transient response characteristic. For this reason, the conventional stepping motor is provided with an inertia damper at its rotary shaft to control an inertia moment which acts on the rotary shaft.
Such an inertia damper is available as an electrical type and a mechanical type, and the electrical type inertia damper is based on a capacitor damping system or a magnetic mounting system and the mechanical inertia damper uses an elastic member or a viscous fluid.
The mechanical inertia damper using an elastic member is disclosed in Japanese Patent Gazette for Laid Open No. SHO 61-9156 and the damper using viscous fluid is disclosed in Japanese Patent Gazette for Laid Open No. SHO 58-123362.
Of the above mechanical inertia dampers, however, the inertia damper using the elastic member is provided with an elastic member made of an elastic material such as, for example, rubber as a fitting means between the mounting base fixed on the rotary shaft and the inertia weight component and therefore accompanies a problem that a repulsive elasticity is produced in an elastic member when the inertia moment is absorbed and a new vibration may be produced by this repulsive elasticity and the damper is inferior in absorptivity of inertia moment. The inertia damper using a viscous fluid also accompanies a problem that an oil seal for sealing the fluid is required and production costs are high due to strict machining accuracy.